Copper complexes biguanide

The bivalent metals, as usual, combine with two molecules of biguanide to form 4-coordinated planar complexes, while the trivalent cobalt and chromium combine with three molecules of the ligand to produce a 6-coordinated octahedral configuration. The only exception is the trivalent silver which yields, however, a 4-coordinated planar complex. The preparation of the free tris(biguanidato) chromium, Cr(C2N5H6)s, in the anhydrous state,6 as well as of the corresponding anhydrous cobalt(III),8 copper(II), cobalt(II), palladium(II), and nickel(II) compounds, provides indisputable evidence for the structure proposed. Similar anhydrous metallic complexes with numerous substituted biguanides also have been included in the above-mentioned studies. 

Cu(HOsSC6H4C2N6H6)2] Copper-(II) complexes of 1-phenyl-biguanide-p-sulfonic acid, 7 6 Cul, 6 3... 

In view of the strong colours of many of the biguanide complexes, these have been used as colorimetric reagents, e.g. the use of phenylbiguanide for spectrophotometric determination of Fe and CN ions. A polarographic study" of a bis(biguanide)copper(II) complex gives a kinetically controlled wave prior to a two-electron transfer, followed by a diffusion controlled second wave due to the reduction of bis species in solution. 

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